1. Field of the Invention
The present invention relates to a microlens array, to a manufacturing method for the microlens array, and to a display device using the microlens array.
2. Description of the Related Art
Microlens arrays comprising a large number of very small lenses arranged in an ordered pattern have been used in liquid crystal display (LCD) panels and other applications. Using a microlens array in an LCD panel makes it possible for each lens to focus incident light on an individual pixel, and thereby achieve a bright display.
Microlens arrays can be manufactured using dry etching and wet etching methods. A drawback to both dry and wet etching methods is the need for a lithography step in the production of each microlens array, thus increasing manufacturing cost.
To resolve this problem, Japan Unexamined Patent Application Publication (kokai) 3-198003 teaches a method for manufacturing a microlens array without using a lithography step. This method uses a master having formed thereon curved surfaces corresponding to each of the lenses in the microlens array. A resin is then deposited on this master, set, and removed from the master to obtain the microlens array.
While the microlens array is used to achieve a brighter display screen, the light gathering power of each lens is not always sufficient. It is therefore desirable to further increase screen brightness.
Therefore, it is an object of the present invention to overcome the aforementioned problems.
With consideration for this problem, an object of the present invention is to provide a microlens array achieving a brighter display screen.
A further object of the present invention is to provide a method for manufacturing this microlens array.
Another object of the present invention is to provide a display device using a microlens array according to the present invention.
To achieve the above objects, a microlens array manufacturing method according to the present invention comprises a step for forming a light transmitting layer from a light transmitting layer precursor by pressing together a first master and a second master with the light transmitting layer precursor disposed between the first and second masters. The first master has a plurality of first curved surfaces, and the second master has a plurality of second curved surfaces. The resulting light transmitting layer has on both sides thereof a plurality of lens surfaces formed in the light transmitting layer precursor by the first and second curved surfaces on the masters.
By thus compressing a light transmitting layer precursor between first and second masters, the curved surfaces formed on the surfaces of the first and second masters are transferred to the light transmitting layer precursor to form lens surfaces. A microlens array having a plurality of lens surfaces on both sides can thus be easily manufactured.
With a microlens array thus having lenses on two sides, incident light is gathered twice, thereby achieving a brighter display.
Furthermore, once manufactured, the first and second masters can be reused multiple times insofar as their durability allows. The steps for manufacturing the microlens array masters can thus be omitted for second and subsequent microlens arrays, thereby reducing the number of production steps and production cost.
In this exemplary manufacturing method, the first and second masters are preferably positioned with respect to each other with the center axis of each first curved surface aligned with the center axis of a corresponding second curved surface, and the masters are then pressed together with the light transmitting layer precursor disposed therebetween.
By thus aligning the masters, the center axes of corresponding lens surfaces are aligned in the resulting microlens array.
Yet further preferably, a second light transmitting layer is formed from a second light transmitting layer precursor on at least one side of the first light transmitting layer.
This second light transmitting layer forms a protective layer over the lens surfaces on the side of the first light transmitting layer to which it is formed. The interface between the first light transmitting layer and this second light transmitting layer then becomes the lens surface.
Yet further preferably, the second light transmitting layer is formed by compressing the second light transmitting layer precursor between the first light transmitting layer and a third master. This third master has raised parts forming a plurality of areas between the raised parts so that recessed parts are formed from the raised parts in the second light transmitting layer. This microlens array manufacturing method further comprises: a step for separating the third master from the second light transmitting layer; and a step for forming a light shield layer by filling the recessed parts in the second light transmitting layer with a light shield material.
A microlens array obtained by this manufacturing method further comprises a light shield layer formed by filling recesses transferred to the second light transmitting layer from raised parts (i.e. projections) in the third master with a light shield material. This light shield layer forms a black matrix whereby contrast between adjacent pixels can be improved.
A microlens array manufactured according to this exemplary method of the present invention achieves a bright screen and improves image contrast, and can be easily manufactured with a simple transfer molding process.
Yet further preferably, in the step for forming the second light transmitting layer in this method, the third master is aligned so that the center axis of each lens surface formed in the light transmitting layer is surrounded by raised parts of the third master.
By thus positioning the third master, the recesses transferred to the second light transmitting layer from the convex parts of the third master are formed to surround the center of each lens surface. As a result, a black matrix is formed away from the lens surface centers.
A microlens array manufacturing method according to the present invention further preferably comprises a step for forming a light shield layer by filling with a light shield material recessed parts of a third master having recessed parts defining a plurality of areas; and a step for separating the third master from the light shield layer and second light transmitting layer. In this case the step for forming a second light transmitting layer compresses the second light transmitting layer precursor between the first light transmitting layer and this third master after the recesses therein are filled with the light shield material.
A microlens array thus comprised has a light shield layer formed by the light shield material filled into the recesses in the third master such that the light shield layer is molded integrally with a light transmitting layer. This light shield layer forms a black matrix whereby contrast between pixels can be improved.
A microlens array manufactured according to this exemplary method of the present invention achieves a bright screen and improves image contrast, and can be easily manufactured with a simple transfer molding process.
Yet further preferably in this case, the third master is aligned so that the center axis of each lens surface formed in the light transmitting layer is surrounded by recessed parts of the third master in the step for forming the second light transmitting layer in this method.
By thus positioning the third master, the light shield layer formed in the recessed parts of the third master is aligned so that the center of each lens surface is surrounded by light shield material. As a result, a black matrix is formed away from the lens surface centers.
In a manufacturing method according to the present invention, the recessed parts are preferably filled with light shield material using an ink jet method.
Ink jet methods enable the light shield material to be injected into the recesses quickly and without waste.
Yet further preferably, the above methods of the present invention further comprise a step for forming a third light transmitting layer over the light shield layer.
This third light transmitting layer covers and protects the light shield layer, and smoothes the surface on which the light shield layer is formed.
The present invention further relates to a microlens array manufactured using any of the methods of the present invention.
A microlens array according to the present invention further relates to a microlens array having a light transmitting layer with a plurality of first lens surfaces formed on one side thereof, and a second lens surface aligned with an optical axis of each first lens surface formed on the other side of the light transmitting layer.
A microlens array according to the present invention thus has lenses on two sides formed so that light incident upon lenses on one side is gathered twice, thereby achieving a brighter screen.
Yet further preferably, a microlens array according to the present invention comprises a second light transmitting layer on at least one side of the above-noted light transmitting layer.
This second light transmitting layer forms a protective layer over the lens surfaces on the side of the first light transmitting layer to which it is formed. The interface between the first light transmitting layer and this second light transmitting layer then becomes the lens surface.
Yet further preferably, a microlens array according to the present invention additionally comprises a light shield layer formed on at least one side of the light transmitting layer so that the center axis of each lens surface is surrounded by the light shield material of the light shield layer.
The resulting light shield layer surrounding the lens centers forms a black matrix, thus improving contrast between pixels.
The present invention further relates to a display apparatus comprising a microlens array according to the present invention, and a light source for emitting light to the microlens array.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.